Analysis and Design of an Axial Flux Permanent Magnet Motor for in-Wheel System Using a Novel Analytical Method Combined With a Numerical Method

Recently, a motor for an in-wheel system—which is advantageous when applied to electric vehicles and self-driving systems—has received much attention. In this paper, we propose an analysis and design method that can be used for an in-wheel motor. In-wheel motors require high torque density and a compact form factor to be wheel-mounted. To meet these requirements, an axial flux permanent magnet motor is proposed for the in-wheel system. The end-winding length of the coil is a key factor to be considered in this design. Hence, we propose a novel method to study the end-winding length. Due to the structural characteristics of an axial flux permanent magnet motor, a three-dimensional finite element analysis, which requires much time and expense, is essential. To solve this problem, we propose a novel analytical method combined with finite element analysis to mitigate the time and cost factors in the development of the axial flux permanent magnet motor. The magnetic saturation and the slot opening effect, which are considered during the analysis and design phase, are extremely difficult to analyze due to their nonlinearity. Therefore, a novel analytical method and algorithm, which can consider nonlinear effects, such as the magnetic saturation and slot opening, is proposed. The usefulness of the proposed analysis and design method and the axial flux permanent magnet motor for an in-wheel system were verified via 3D finite element analysis using a commercial simulation tool (JMAG).